Temperature‐Dependent CO₂ Electroreduction over Fe‐N‐C and Ni‐N‐C Single‐Atom Catalysts

Abstract

Reaction temperature is an important parameter to tune the selectivity and activity of electrochemical CO₂ reduction reaction (CO₂ RR) due to different thermodynamics of CO₂ RR and competitive hydrogen evolution reaction (HER). In this work, temperature-dependent CO₂ RR over Fe-N-C and Ni-N-C single-atom catalysts are investigated from 303 to 343 K. Increasing the reaction temperature improves and decreases CO Faradaic efficiency over Fe-N-C and Ni-N-C catalysts at high overpotentials, respectively. CO current density over Fe-N-C catalyst increases with temperature, then gets into a plateau at 323 K, finally reaches the maximum value of 185.8 mA cm^-2 at 343 K. While CO current density over Ni-N-C catalyst achieves the maximum value of 252.5 mA cm^-2 at 323 K, and then drops significantly to 202.9 mA cm^-2 at 343 K. Temperature programmed desorption results and density functional theory calculations reveal that the difference of temperature-dependent variation on CO Faradaic efficiency and current density between Fe-N-C and Ni-N-C catalysts results from the varied adsorption strength of key reaction intermediates during CO₂ RR.